The present invention relates to molecular biology and more specifically to nucleic acids and the proteins encoded by them. Invention nucleic acids encode novel ataxin-2 binding proteins. The invention also relates to methods for making and using such nucleic acids and proteins, for example, to treat particular pathologies.
Numerous pathologies characterized by abnormal or undesirable cell death or cell growth are the result of abnormal gene expression or activity. Cellular degenerative and hyperproliferative disorders such as Alzheimer""s disease and cancer are two particular examples. Although several genes that contribute to degenerative and hyperproliferative disorders have been identified, the signal transduction pathways which mediate the development of such disorders presently are not well understood.
Spinocerebellar ataxia type-2 is one example of a group of clinically similar late onset hereditary degenerative disorders affecting the brain and central nervous system. A single gene SCA2, located on chromosome 12, has been linked to development of spinocerebellar ataxia type-2; SCA2 encodes ataxin-2, a 140 kDa protein whose function is presently unknown. Clinically similar neurodegenerative disorders include, for example, spinocerebellar ataxia types 1 and 6, spinobulbar muscular atrophy, Huntington disease and Machado-Joseph disease (Trottier et al., Nature 378:403-406 (1995)). Although the development of these similar disorders are mediated by distinct genes, a shared genetic alteration initiates onset of the pathologies. In the case of spinocerebellar ataxia type-2, for example, afflicted individuals exhibit expansion of a CAG trinucleotide in SCA2 and a corresponding increase in the number of glutamine residues in the encoded ataxin-2 protein (Pulst et al., Nat. Genet. 14:269-276 (1996)). Typically, afflicted individuals have a polyglutamine sequence of about 35-39 residues, whereas normal individuals have about 22 contiguous glutamine residues in ataxin-2. Similarly, CAG repeat expansion in genes linked to spinocerebellar ataxia types 1 and 6, spinobulbar muscular atrophy, Huntington""s disease and Machado-Joseph disease correlate with the development of these disorders. As a result of this shared genetic alteration, these pathologies are collectively referred to as glutamine repeat disorders.
In spite of this genetic knowledge, the function of genes, such as SCA2 in general, and the role of CAG repeat expansion and corresponding glutamine sequence expansion in the development of degenerative disorders such as spinocerebellar ataxia type-2 in particular, is not understood. In this regard, the glutamine repeat sequence of SCA3 in normal individuals is in the same size range as that of the glutamine repeat sequence of SCA2 in individuals afflicted with spinocerebellar ataxia type-2. Similarly, the molecular components that regulate or mediate cellular degeneration, and the mechanism by which they participate in this signal transduction pathway, are not understood.
Thus, a need exists to identify and characterize the molecular components that participate in this signal transduction pathway, such as proteins that bind to ataxin-2 in vivo. Moreover, a need exists to identify the nucleic acid and amino acid sequences of the respective genes and gene products, their activities, and the functional domains of such binding proteins. To the extent that such molecules are identified, they can form the basis for the development of diagnostic protocols or clinical therapies useful for the diagnosis or treatment of disorders characterized by cellular degeneration or hyperproliferation. The present invention satisfies this need and provides related advantages as well.
In accordance with the present invention, there are provided novel isolated nucleic acids encoding ataxin-2-binding proteins (A2BPs), or functional fragments thereof. The invention also provides vectors containing invention nucleic acids and recombinant cells transformed therewith, antisense-nucleic acids thereto and related compositions. Further provided are oligonucleotides capable of hybridizing with an invention nucleic acid, such oligonucleotides further being labeled. Invention nucleic acids described herein are useful as probes for assaying an amount of A2BP mRNA in a sample and for identifying nucleic acids encoding a A2BP. Invention nucleic acids also are useful for expression in cells for the purposes of identifying agonists or antagonists of A2BP function.
In accordance with the present invention, also provided are novel isolated ataxin-2-binding proteins (A2BPs) having ability to bind to ataxin-2 or having ability to bind to a nucleic acid molecule. Methods for expression of A2BP or functional fragments thereof additionally are provided. Proteins or fragments thereof are useful in bioassays, as therapeutic compositions, and as immunogens for producing anti-A2BP antibodies. Also provided are transgenic non-human mammals that express invention A2BP and mutants thereof. Transgenic non-human mammals that do not express an endogenous A2BP additionally are provided.
Antibodies having specific reactivity with A2BP also are provided. These antibodies are useful for detecting A2BP in a sample in diagnostic assays, or for identifying genes encoding proteins having similar immunoreactivity to A2BP. Invention antibodies also can be used to purify a A2BP from biological fluid, tissues, cells, and the like.
Methods for identifying A2BP binding proteins also are provided. A method comprises contacting a sample containing a A2BP binding protein and identifying the protein that binds thereto. Also provided are methods for identifying a nucleic acid molecule that binds to A2BP. A method comprises contacting a sample containing nucleic acids and identifying a nucleic acid molecule that binds thereto.
Methods for modulating the activity of a protein or RNA that binds A2BP also are provided. A method comprises contacting a A2BP binding protein or nucleic acid molecule with a substantially pure A2BP, or functional fragment thereof. A method of modulating the activity of ataxin-2 also is provided.
Methods of treating a degenerative or hyperproliferative disorder are provided. A method of the invention employs an antisense A2BP nucleic acid in an amount effective to inhibit expression of a human A2BP. A method also employs A2BP or functional fragment thereof or agonists or antagonists thereto administered to a subject.